Industrial scientific medical (ISM) frequency bands are used in biomedical applications.
One particular band of interest, which provides a good compromise between in-body loss and antenna efficiency, falls in the 902-928 MHz frequency range and has quite limited bandwidth. For high quality imaging application with typical resolution of 640×480 pixels and frame rate of 10 fps, both bandwidth efficient modulation scheme and high ratio of image compression are needed.
Datasheet ZL70250 from Zarlink Corporation and A. C. W. Wong, G. Kathiresan, C. K. T. Chan, O. Eljamaly, O. Omeni, D. Mcdonagh, A. J. Burdett and C. Toumazou, “A 1V wireless transceiver for an ultra-low-power SoC for biotelemetry applications,” IEEE J. Solid-State Circuits, vol. 43, No. 7, pp. 1511-1521, July 2008 disclose wireless transmitters employed in biomedical imaging applications that adopt frequency shift keying (FSK) modulation schemes. However, the data rate of these two transmitters is limited to a few Mbps, due to their bandwidth modulation schemes.
Y.-H. Liu, C.-L. Li and T.-H. Lin, “A 200-pJ/b MUX-based RF transmitter for implantable multichannel neural recording,” IEEE T. on Microwave Theory and Techniques, vol. 57, pp. 2533-2541, October 2009 discloses a transmitter used for neural recording application that employs an orthogonal quadrature phase shift keying (O-QPSK) modulation scheme that can achieve data rate up to 17.5 Mbps. However, the system complexity limits the achievable power consumption level.
There is thus a need to have a transmitter with simple architecture, which enables high data rate transmission and consumes low power.